This invention relates to an actuating mechanism for a lip barrier on a dock leveler. Several techniques of providing a run-off barrier at the outer end of a dock leveler are known in the art. The simplest method is to extend the rear edge of the folding lip so that a barrier is raised when the lip is folded in the stored or pendant position, and is lowered when the lip is extended. This method is sometimes known as the "Post Office" lip barrier because it is often specified by the United States Postal service. Although simple in operation, it has a limitation in that it restricts access to the transport trailer when the lip is stored to allow "end loading". This is the condition in which the placement of cargo at the rear of the trailer is accomplished without having the lip rest on the bed of the trailer.
Other devices which allow the barrier to be lowered for end loading are known, such as shown in U.S. Pat. No. 4,920,598 but they require complex structure, expensive machined parts, and they still have limitations. For example the device shown in the '598 patent cannot lower the barrier when the dock leveler is stored unless safety legs are provided, and a means to allow the operator to activate the legs must be provided. Conversely, the barrier cannot be raised when the dock leveler is fully lowered for below-dock end loading, although the chance of a run-off accident is greatly increased when the dock leveler is in a declined, i.e. downwardly sloping position. In addition, because the lip is carried by lip keepers when the dock leveler is stored, the significant change in weight carried by the dock leveler restricts its use to hydraulic dock levelers. Some barriers are connected directly to the lip and have the same limitations as the Post Office lip.
Others can be actuated independently but require an external actuator such as a hydraulic cylinder to raise them.